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Geography physical > The restless Earth > Flashcards

The restless Earth Flashcards

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1
Q

Describe inner core

A

hottest part of earth
solid iron and nickel
up to 5,500 degrees c

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2
Q

describe outer core

A

liquid iron and nickel

similar temperatures to inner core

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3
Q

Describe mantel

A

widest section of earth
thickness= approx 2,900km
molten

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4
Q

describe crust

A

thin - 0-60km

solid rock

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5
Q

Compare continental crust with oceanic crust

A

C = lower density, mainly granite rock, thicker (50-60km), older (4 billion years)

O = higher density, mainly basalt rock, thinner (6-9km), younger (200 million years)

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6
Q

What generates convection current?

A

radioactive decay in core

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7
Q

How does convection current happen?

A

hot, less dense rises

cold, more dense falls

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8
Q

What moves tectonic plates?

A

convection currents

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9
Q

What is a destructive plate boundary?

A

plates move towards each other

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10
Q

What do destructive plate boundaries cause?

A

violent volcanoes, earthquakes, deep-ocean trenches and fold mountains.

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11
Q

Describe what happens in destructive plates

A
  1. Ocean ice plate less dense so is forced under continental plate, point at which this happens is called subduction zone.
  2. Oceanic plate melts due to friction and increased temp, magma forms resulting in earthquakes.
  3. Magma collects to form magma chamber. Magma then rises up through cracks in continental crust. Building pressure can cause volcanic eruption.
  4. Continental crust squashed and forced upwards, creating fold mountains.
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12
Q

Give an example of destructive plate boundary

A

Nazca plate forced under South America plate, resulting is Andes mountain range

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13
Q

What is a constructive plate boundary?

A

plates moving apart

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14
Q

What do constructive plate boundaries cause?

A

less violent volcanoes and earthquakes and mid ocean ridges

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15
Q

Describe what happens in constructive plate boundaries

A
  1. Plates move apart so magma rises from mantel and onto surface. Earthquakes occur.
  2. Magma on surface cools and solidifies, forming new crust of igneous rock. Repeats over time and eventually builds up to form shield volcano.
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16
Q

Give example of constructive plate boundary

A

North American plate moving away from Eurasian plate, resulting in mid Atlantic ridge and formation of Iceland through volcanic activity

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17
Q

What is a conservative plate boundary?

A

Plates slide past one another

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18
Q

What do conservative plate boundaries cause?

A

frequent and violent earthquakes

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19
Q

Describe what happens in conservative plate boundary

A
  1. plates often become stuck due to opposing directions or different speeds.
  2. Pressure builds up and causes earthquakes when released.
20
Q

example of conservative plate boundary

A

San Andreas fault - North American plate and Pacific plate moving in same direction but at different speeds

21
Q

What is a collision margin?

A

two continental crust collide and neither can sink

22
Q

What happens in collision margin?

A
  1. plates push into eachother, forcing material to be folded up into huge mountain ranges. Pressure may also cause earthquakes
23
Q

example of collision margin

A

Indian plate collided with Eurasian plate to form Himalayas

24
Q

where do fold mountains form?

A

destructive and collision plate boundaries

25
Q

Describe formation of fold mountains

A
  1. sediments accumulate in geosynclines
  2. As plates move together, rocks start to form folds which have anticlines and synclines. These are pushed upwards to form fold mountains
26
Q

What is the case study for fold mountains?

A

the Alps

27
Q

Describe the case study for fold mountains

A

Alps.

location: Central Europe
Formation: African plate collided with Eurasian plate

uses:

farming - cattle and sheep on mountains and crops of valley floor

Tourism - winter sports e.g. skiing

HEP - steep terrain, high rainfall and snowmelt = lots of water to HEP plant. HEP in Alps provides 60% Switzerlands energy

Mining - previously used to salt, iron ore, gold, silver and copper mining but cheaper competition and meant companies leave Alps.

Adaptations:

Farming - use technology to reduce transhumance. Farming space decreases and tourism increases so new methods e.g vineyards on sunny, South facing slopes

tourism - stable income all year by introducing summer activities eg hiking and climbing

28
Q

Where do volcanoes form?

A

destructive and constructive plate boundaries

29
Q

describe formation of volcanoes

A
  1. magma rises through cracks/weaknesses in Earths crust.
  2. pressure builds up inside Earth
  3. magma explodes to surface when pressure released, causing volcanic eruption
  4. lava from eruption cools on surface to form new crust
  5. this process repeats over time and rocks builds up to form volcano.
30
Q

Describe the inside of a volcano.

A

Magma chamber - collection of magma inside earth

main vent - main outlet for magma to escape

secondary vents - smaller outlets for magma to escape

crater - created after eruption blows top off volcano.

31
Q

What is a active volcano

A

erupts frequently

32
Q

what is a dormant volcano

A

temporarily inactive but not fully extinct

33
Q

what is an extinct volcano

A

never likely to erupt again

34
Q

Where are shield volcanoes located?

A

constructive ate boundaries

35
Q

how are shield volcanoes formed?

A

eruptions of thin, runny lava

36
Q

Characteristics of shield volcanoes

A

low
gentle sloping sides
frequent but gentle eruptions

37
Q

location of composite volcanoes

A

destructive plate boundaries

38
Q

characteristics of composite volcanoes

A

made up of alternating layers of lava and ash

eruptions may be a pyroclastic flow

39
Q

what is a pyroclastic flow?

A

mixture of hot steam, ash, rock and dust. high speed and temperatures of 400+ degrees

40
Q

give positive effects or eruptions

A

dramatic scenery created which attracts tourists

lava and ash deposited breaks down to provide nutrients for soil

geothermal energy

41
Q

give negative effects of eruptions

A

loss of lives

landscape can be destroyed forever

Lahars can be created if ash and mud mix with water

42
Q

what is a lahar

A

fast moving mudflow

43
Q

What is the case study of volcanic eruption

A

Chances Peak, Monserrat (1995-97)

44
Q

Name the layers of the earth in order

A

Inner core
Outer core
mantel
crust

45
Q

Describe case study of volcanic eruption

A

Location: small island in Caribbean

Before 1995 it had been dormant for over 300 years

warning signs of eruption in 1995

effects:

19 people killed
Homes and buildings destroyed including hospital and transport links
Plymouth (Capitol City) covered in mud and ash

Short-term responses:

Geography physical (1 decks)

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